a) Field of the Invention
The invention is directed to an electronic level with a clinometer and a process for video sighting or targeting of a graduated staff of at least one target at a distance, from the level in accordance with the preamble of the first patent claim, wherein the level, as a dumpy level or quickset level, has a high degree of automation at low manufacturing cost.
b) Description of the Related Art
DD 291 141 discloses an arrangement for leveling the line of sight of levels, wherein the arrangement comprises a telescope with a sighting axis, including an objective with sliding lens, a graticule and an eyepiece. The arrangement further contains a photoreceiver device with a differential photoelement and a piezo-actuator by means of which the graticule can be adjusted in such a way, depending on the signals which are supplied by a clinometer and appropriately processed by a microprocessor, that a leveling of the telescope axis is achieved.
JP 60-25 413 describes a level with a digital graduated staff at the target. In this case, a light beam is sent to the graduated staff via a beam splitter from a light source arranged in the level and an image of the graduated staff is received by an optical television camera system and displayed on a screen. The determined data are stored in a computer and evaluated in a suitable manner. The screen itself is a liquid crystal display with elements arranged in a matrix. The objective can be focused manually by a sliding lens.
Further, JP 5-272 970 discloses an automatic level which comprises a matrix receiver with a screen, wherein image signals from a CCD-camera are converted into corresponding digital signals by an analog-to-digital converter and are stored in a data storage. The CCD-camera has a focusable objective with a sliding lens.
In the above-mentioned arrangements, focusable objectives are always provided for sharp imaging of the staff graduation on a photoreceiver arrangement or CCD arrangement.
In order to do without focusing, a device for leveling purposes (DE 195 04 039 C1) was provided with imaging optics and a spatially-resolving optoelectronic detector for image recording. In this case, the imaging optics are divided into pupil zones imaging in different ways for different depth of focus ranges; different partial areas of the detector are allocated to the pupil zones. While this device does avoid focusing, the different imaging optics are relatively uneconomical.
In a process for geometric height measurement according to DE 39 16 385, in a manner analogous to the signals of a clinometer arranged in a measurement device independent from a telescope, the reference point for the horizontal position of the measurement device is provided on the center pixel of a CCD array and, when the device is tilted, is displaced in such a way that its position corresponding to the respective inclination of the device determines the intersection point of the horizontal sighting axis for a pixel or for the area between two pixels.